1. Technical Field
The present disclosure relates to a method for packing a powder material of a compact into a die cavity of a die used for molding a compact.
2. Description of Related Art
In the technology of compression-molding a powder material, such as a metal powder, with a die into a compact of a desired shape, attempts have been hitherto made to achieve a uniform density of the molded compact by contriving a method for packing the powder material into a die cavity of the die (e.g., see Japanese Patent Application Publication No. 2002-192391 and Japanese Patent Application Publication No. 4-210896). The packing density of the powder material varies according to the manufacturing process, management conditions, etc. thereof, and especially when the manufacturing lot of the powder material is changed, the packing density can change significantly. Therefore, to produce a compact having a desired strength or packing density, it is necessary to adjust the amount of packing (packing depth) of the powder material in the die according to the packing density of the powder material. For example, FIG. 4 shows a state where a powder material M is packed in a die cavity 36 of a die of which heights of a die plate 34 and a lower inner 38 relative to each other are adjustable. In the example of FIG. 4, the position of the die plate 34 is adjusted so that an upper surface 34a of the die plate 34 is located at a position higher than the position of an upper surface 38a of the lower inner 38. As a result, a difference in height (submersion depth) indicated by reference sign H is left between the die plate 34 and the lower inner 38. In the example of FIG. 4, to pack the powder material M into the die cavity 36 of the die, a holder 12 that holds the powder material M is brought into sliding contact with the upper surface 34a of the die plate 34, with a bottom surface of the holder 12 open, and the holder 12 is advanced and retracted over the die cavity 36.